API Testing — Deep Dive

API Testing — Deep Dive is a skill for Claude Code, Codex from ShulkwiSEC/bb-huge. It costs 25 tokens per session (1,006 once invoked), scanned A, original, MIT.

A step-by-step guide to testing web APIs with PortSwigger’s security labs, including example requests and payloads for different lab variations.

In plain words
What is it for?
Use it to study API documentation exposure, hidden or unused endpoints, extra parameters sent between services, filter bypasses, and chains of security flaws in Burp Suite.
Why use it?
It gives you a structured way to practise finding API weaknesses instead of piecing techniques together from scattered notes. It is aimed at authorised security testing, such as lab work, certification preparation, or bug bounty programs.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/shulkwisec/bb-huge/api-testing-labs
Any agent
npx skills add ShulkwiSEC/bb-huge --skill api-testing-labs
Clone the repo
git clone --depth 1 https://github.com/ShulkwiSEC/bb-huge

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for API Testing — Deep Dive

README.md
[![agentmods](https://agentmods.dev/badge/skills/shulkwisec/bb-huge/api-testing-labs.svg)](https://agentmods.dev/skills/shulkwisec/bb-huge/api-testing-labs)
Your own site
<a href="https://agentmods.dev/skills/shulkwisec/bb-huge/api-testing-labs"><img src="https://agentmods.dev/badge/skills/shulkwisec/bb-huge/api-testing-labs.svg" alt="Measured on agentmods" height="20"></a>
Per session 25 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,006 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00025 $0.01006
Opus 5 $0.00013 $0.00503
Sonnet 5 $0.00005 $0.00201
Haiku 4.5 $0.00003 $0.00101

Measured 3d ago against content hash 1cb8004c00b9, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

API Testing — Deep Dive scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/process.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

tools: [burp-suite, curl, sqlmap, ffuf, python, hashcat, ysoserial]
Origin

Copies of this mod

2 near-identical copies found in the catalogue:

skills/curated/api-testing-labs/SKILL.md · 127 lines

How it starts

The opening of the file, as written. The whole thing — 127 lines — stays where its author put it; the contents beside it link to each section on GitHub.

API Testing — Deep Dive

Deep-Dive Lab Playbook — Every PortSwigger lab variant with exact payloads, bypass techniques, and zero-day extensions. 🟢 Apprentice 🟡 Practitioner 🔴 Expert

When to Use

  • BSCP certification prep
  • Real-world bug bounty hunting
  • Building exploitation chains
  • Understanding bypass techniques

Prerequisites

  • Burp Suite Professional
  • Burp Collaborator / interactsh
  • Browser with proxy configured

Workflow

Phase 1: Reconnaissance

  • Identify input vectors, parameters, and application behavior.

Phase 2: Exploitation

  • Apply standard lab payloads.

Phase 3: Zero-Day Escalation

  • Fuzz filters, bypass WAFs, and chain with other vulns.

Lab Playbooks

Lab 1: Exploiting documentation 🟢 APPRENTICE

Find /api docs endpoint → discover /api/user/carlos DELETE endpoint → delete user.

Lab 2: Server-side param pollution query 🟡 PRACTITIONER

POST /forgot-password HTTP/1.1

username=administrator%26field=reset_token

%26 = & → injects additional parameter into server-side API call → leaks reset token.

Lab 3: Unused API endpoint 🟡 PRACTITIONER

Change GET /api/products/1/price to PATCH method:

{"price":0}

→ Buy product for $0.

Lab 4: Mass assignment 🟡 PRACTITIONER

{"chosen_discount":{"percentage":100}}

Include discount object in checkout request → 100% discount applied.

Lab 5: Param pollution REST URL 🟡 PRACTITIONER

username=administrator#

Server constructs: /api/users/administrator#/field# truncates path → returns full user object with token.

Blue Team Detection

  • Monitor access logs for anomalous payloads.
  • Implement strict input validation and parameterized queries where applicable.
  • Create WAF rules masking generic attack patterns.

Zero-Day Research

When standard technique fails:

  1. Identify the filter/WAF
  2. Fuzz with Burp Intruder custom wordlists
  3. Search GitHub/Twitter for new bypasses
  4. Chain with other vulns for escalation
  5. Try encoding variants: URL, double-URL, unicode, hex

Read the full file on GitHub · 127 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 127 lines · 25 tokens per session scan A 1cb8004c00b9

Subscribe to this mod's changes

API Testing — Deep Dive is a skill published in the GitHub repository ShulkwiSEC/bb-huge (21 stars, last pushed 1mo ago), licensed MIT. It adds 25 tokens to every session and 1,006 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.